One of the goals of plant genetic engineering is to produce plants with agronomically desirable characteristics or traits. The proper expression of a desirable transgene in a transgenic plant is one way to achieve this goal. Regulatory elements such as promoters, leaders, and introns are non-coding polynucleotide molecules which play an integral part in the overall expression of genes in living cells. Isolated regulatory elements that function in plants are therefore useful for modifying plant phenotypes through the methods of genetic engineering.
Many regulatory elements are available and are useful for providing good overall expression of a transgene. For example, constitutive promoters such as P-FMV, the promoter from the 35S transcript of the Figwort mosaic virus (U.S. Pat. No. 6,051,753); P-CaMV 35S, the promoter from the 35S RNA transcript of the Cauliflower mosaic virus (U.S. Pat. No. 5,530,196); P-Rice Actin 1, the promoter from the actin 1 gene of Oryza sativa (U.S. Pat. No. 5,641,876); and P-NOS, the promoter from the nopaline synthase gene of Agrobacterium tumefaciens are known to provide some level of gene expression in most or all of the tissues of a plant during most or all of the plant's lifespan. While previous work has provided a number of regulatory elements useful to affect gene expression in transgenic plants, there is still a great need for novel regulatory elements with beneficial expression characteristics. In particular, there is a need for regulatory elements that are capable of directing expression of transgenes in transgenic crop plants at high levels and in particular tissues, organs, or during specific developmental stages of plant growth. Many previously identified regulatory elements fail to provide the patterns or levels of expression required to fully realize the benefits of expression of selected genes in transgenic plants.
Eukaryotic translation initiation factor eIF-4A is an ATP-dependent RNA helicase protein that is required for the binding of mRNA to ribosomes. Members of this family have been reported in many species including mouse, Drosophila, yeast, tobacco, Arabidopsis, wheat, and rice (K A Brander, et al. (1995) Biochimica et Biophysica Acta 1261:424–444). We hypothesized that a promoter and other non-coding regulatory elements from an eIF-4A gene would have a constitutive expression pattern and that the promoter and regulatory elements would be useful to direct expression of a transgene such as a glyphosate resistant 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) transgene to produce a glyphosate tolerant plant. The efficient production of glyphosate tolerant plants requires the use of a promoter and regulatory elements capable of directing transgene expression in all tissues including the most sensitive reproductive organs such as anthers and meristem tissues. The present invention thus provides such promoters and regulatory elements isolated from the eukaryotic translation initiation factor (eIF4A) genes of Nicotiana tabacum, Arabidopsis thaliana, and Medicago truncatula. 